Testing-machine



R. H. THURSTON.

Testing Machine.

No. 233,712. Patented Oct. 26, I880.

N. PETERS. PHOTO-LITHQGRAFNER, WASH Nira ROBERT H. THURSTON, OF HOBOKEN, NEW J ERSEY.

TESTING-MACHINE.

SPECIFICATION forming part of Letters Patent No. 233,712, dated October 26, 1880.

Application filed February 18, 1880.

To all whom it may concern Be it known that I, ROBERT H. THURs'roN, of Hoboken, Hudson county, State ofNew Jersey, have invented a new and Improved Construction of Jaws for Holding Test-Pieces; and I do hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawings, which form a part of this specification.

Figure 1 illustrates the test-piece as it is usually formed when the material is to be tested by torsion. The ends a a are held in the jaws of the testing-machine. The smaller portion, I), between is unsupported, and its length and section are given the dimensions of the piece of which it is desired toknow the resistance offered.

Fig. 2 illustrates the usual construction of thejaws ot'the testing-machine, which hold the test-piece. The ends a a insert into the corresponding recesses A A in the jaws. Force is applied, as shown by the arrow F, to revolve the jaw A and the end a of the test-piece, which is held by it, and this force is opposed by a suitable resistance, 1%, given to the other jaw, A, and consequently to its end a of the test-piece.

It is essential that the axis of the test-piece should exactly coincide with the axis of the jaws. To make this adjustment as is now done,

by the insertion of thin plates between the faces of the test-piece and jaws, requires much painstaking, and is rarelyeffected with the requisite exactness.

My improved means for adjustment consist of the centers 0 O in the axis 00 3 of thejaws. One of these may be hacked by a spring, D, which will press that center forward against the end of the test-piece with a force sufficient to hold the test-piece until it be secured. The centers insert into the same holes at the ends of the test-piece that were used when turning up the latter in the lathe. The axis of the jaws must therefore coincide exactly with the center of the test-piece. Should these center holes have been cut off, the test-piece can be recentered in alathe.

For greater convenience in securing the testpieces I use the following construction: The

recesses in thejaws which. receive the ends of the test-piece are considerably enlarged, and are best formed as a slot, T T, extending through the jaws transversely. to the axis, as shown in Figs. 3, 4, 5. When the test-piece is centered, Fig. 3, two wedges, F F, are pressed in between the faces of the test-piece and those of the slot, and thus hold the testpiece so that it cannot yield.

I claim as my invention and desire to secure by Letters Patent l. The combination, with thcjaws of a testing-machine, of the centers 0 O and spring D.

2. The slot T and pair of wedges F F combined, to hold the test-piece, substantially as set forth.

ROBERT H. THURSTON.

Witnesses:

E. H. BOUGHTON, J 0s. WHITNEY. 

